Toenail fungus typically starts as a small white or yellow-brown spot near the tip of the nail. As the infection spreads, the nail thickens, discolors, and begins to crumble or separate from the nail bed. The specific appearance depends on where the fungus enters the nail and how far the infection has progressed.
Early Signs Most People Notice First
The earliest visible change is usually a small discolored spot under the tip of the toenail. It often looks white or yellowish-brown and can be easy to dismiss as a scuff or minor bruise. At this stage, the nail still feels relatively normal in thickness and texture, but it may lose some of its natural shine.
As the fungus grows, yellow streaks or patches spread across the nail plate. The nail starts to look slightly cloudy or opaque in the affected area. Many people first realize something is wrong when they notice the nail lifting slightly away from the skin underneath, creating a gap where debris can collect.
Color Changes and What They Mean
Toenail fungus doesn’t always look the same. The color depends on the type of fungus involved and how it enters the nail.
- Yellow or yellow-white: The most common presentation. The nail thickens and yellows, especially at the tip and sides, with chalky debris building up underneath.
- White, powdery patches: Small speckled or chalky white spots appear on the surface of the nail. The nail feels rough and crumbles easily. This type stays confined to the toenails and tends to affect the top layer of the nail plate.
- Milky white throughout: A less common pattern where the entire nail develops an even, milky discoloration without the typical thickening or debris buildup underneath.
- Yellow-brown or dark brown: Often signals a more advanced infection. The nail becomes opaque and noticeably thickened. In some cases, dense streaks of fungal material appear as dark linear lines within the nail.
- Black or greenish: A greenish tint suggests bacterial involvement alongside the fungus. Dark brown to black discoloration can occur in advanced infections, though a shiny black spot is more likely a bruise than fungus (more on that below).
In people with darker skin tones, toenail fungus can be harder to spot because natural pigmented lines running along the nail (a normal finding in darker skin) can obscure the early color changes. This sometimes leads to a delayed diagnosis and more advanced disease by the time it’s identified.
Texture and Shape Changes
Color shifts are only part of the picture. The physical structure of the nail changes significantly as the infection progresses. The nail thickens, sometimes to the point where it’s difficult to trim with standard clippers. The surface may become ridged, uneven, or pitted rather than smooth.
Debris collects under the nail as the fungus breaks down the tissue between the nail plate and the nail bed. This buildup pushes the nail upward and can make it look raised or humped. The edges of the nail become brittle and ragged, often crumbling when you try to cut them. In advanced cases, the nail may split or partially detach from the nail bed entirely.
A foul smell is common once the infection is well-established, caused by the combination of fungal growth and trapped debris underneath the nail.
What Advanced Infections Look Like
Left untreated, the infection can consume the entire nail. At this stage, the nail is severely thickened, opaque, and yellow-brown throughout. It may be misshapen, curving or growing at odd angles. The nail plate itself becomes so degraded that large sections crumble away, leaving behind a rough, irregular surface.
When the infection reaches the base of the nail near the cuticle, a white discolored area appears at the root and moves outward as the nail grows. This pattern is less common and is sometimes associated with a weakened immune system. The skin around the nail can become inflamed, red, and swollen, especially when yeast rather than a typical fungus is responsible.
Multiple toenails are often affected, since the fungus easily spreads from one nail to its neighbors. The big toe and little toe are the most commonly infected.
Skin Around the Toes
Toenail fungus frequently coexists with athlete’s foot, a fungal infection of the surrounding skin. If you notice nail changes alongside any of these skin symptoms, the two conditions are likely connected:
- Between the toes: Itchy, peeling, cracked skin, most often between the fourth and fifth toes.
- Soles and sides of the feet: A dry, scaly pattern covering the bottom of the foot in a “moccasin” distribution, almost like the skin is peeling in a shoe-shaped area.
- Inner foot: Small fluid-filled blisters, usually along the arch.
The same organisms cause both conditions, and treating only the nail while ignoring the skin (or vice versa) often leads to reinfection.
How to Tell It Apart From a Bruise
A dark spot under the toenail isn’t always fungus. Stubbing your toe, dropping something on it, or wearing tight shoes can cause blood to pool under the nail, creating a bruise that looks similar to a fungal infection.
A bruise typically appears black and shiny, and you can usually recall the injury that caused it. A fungal infection tends to look yellow, gray, or greenish rather than glossy black. The key difference is whether the nail has separated from the skin underneath. If the discolored area looks opaque and the nail seems lifted or detached from the nail bed, that points toward fungus. If the nail is still firmly attached and the dark spot is visible through a clear nail plate, it’s more likely a bruise that will grow out over several months.
How It Differs From Nail Psoriasis
Nail psoriasis and toenail fungus can look remarkably similar, and they sometimes occur together. Both cause thickening, discoloration, and separation from the nail bed. A few visual clues help distinguish them.
Psoriasis tends to produce small, uniform pits scattered across the nail surface, like tiny dents made with a pin. It also causes distinctive salmon or oil-colored spots on the nail bed, a yellowish-red or orange discoloration that looks like a drop of oil under the nail. These features are uncommon in fungal infections. Fungal nails, on the other hand, typically show more crumbling and debris accumulation. Under magnification, a fungal infection shows a jagged, fringed border where healthy nail meets infected nail, while psoriasis often has a more defined edge.
Because the two conditions overlap visually, a lab test is usually needed to confirm whether fungus is present. A nail clipping can be sent for staining or culture, though it’s worth knowing that cultures come back falsely negative in up to 30% of cases. A nail biopsy with special staining is the most accurate method.
Which Toenails Are Most Affected
Fungal infections overwhelmingly favor toenails over fingernails. Toes spend more time in warm, moist environments inside shoes, and they grow slowly, giving the fungus more time to establish itself. The big toenail is the single most common site, partly because its larger surface area provides more room for the fungus to take hold and partly because it sustains the most repetitive pressure from walking and footwear.
The infection almost always starts at the free edge of the nail (the tip you trim) or along the sides, then gradually works its way back toward the cuticle. By the time the entire nail is involved, the infection has typically been present for months or even years.